OK... a lot of our trucks have hydroboost pumps for steering and brakes.

I hate the electric brakes on our 5er. I do a lot of mountain towing and I have bought but not installed an exhaust brake. I've got a 6 speed manual.

I've been thinking of going to one of those hydraulic disk brake systems on our trailer, but they are kind of costly. The pump is pretty expensive. I still don't know how those systems are modulated and people tell me the brake action has an awful lag to it.

Why couldn't I put hydraulic brakes on the trailer and use the rear hydraboost brake circuit to power it ? One could mount a small hydraulic quick coupler to the back of the truck and just plug the trailer into the truck. Only thing is, how would one do the brake away brakes ? One could use a hydraulic accumulator and some fancy valves ? If you lost pressure on the supply hose, the brakes would jam on. How would one modulate the brakes ? If you hooked into the rear brake circuit the pressure on it is modulated already, but then how would you do the break away system ?

Big Chevy trucks (C65) that have hydraulic brakes have an accumulator and an electric pump in case the engine quits.

Any ideas ?

 

First thing you should do is install the exhaust brake, you will like it in the mountains.

You can buy a electric over hydraulic actuator to do about the same thing you are talking about.

 

It would have to be a third leg off the hydroboost. Rear circuit can hardly handle the rear brakes...

If you really want awesome brakes, do vacuum brakes. the trucks vacuum pump can handle it fine and they are the next best thing to air brakes. Probably cost you about the same as trying to do hydraulic disc brakes.... its at least something to look into.... there may even be someone on here that will give/sell you the truck side setup for vacuum brakes if they bought a truck with it and dont need it....

-Trey

 

I second the vacuum brakes. You can find information on them at Velvac.
Also try:Low Cost Trailer Supply

Hyspeed

 

By my diesel doesn't have a vacuum pump.

Do you think it is worth putting one on just to run trailer brakes ?

The newer Dodge and Ford trucks use hydroboost and they don't have vacuum.

 

You would have to have a vacuum pump installed.

A buddy of mine has a Freightliner FL 60 with a vacuum trailer brake system that has it's own vacuum pump. The truck has hydraulic brakes that run off the power steering pump with an electric motor back-up. His present trailer had electric brakes but he replaced those with electric/hydraulic. I would have thought that he would have gone with the vacuum but you can't tell him anything. Now he is having trouble getting his brake controller to work correctly with the hydraulic unit. This is a 3 axle 40' 5th wheel camper and he had to convert all the backing plates and shoes from electric to hydraulic.

Right now there's no belt on the vacuum pump on his truck, what a waste.

Hyspeed

 

"Now he is having trouble getting his brake controller to work correctly with the hydraulic unit."

I've heard the same thing.

I don't know anything about vacuum brake systems for a trailer. I imagine it uses a master cylinder like on a truck why vacuum brakes ? How does it hook up to my brake pedal ?

 

I from experience highly do not recommend electric over hydraulic systems. Period!

 

if you have no vac pump, you could go air.... i mean if you are to install one pump or the other..... might as well have onboard air at that point....

 

Well, I need either vacuum or air pressure to run my exhaust valve.

How does one put air over hydraulic brakes onto a trailer.

For that matter, how do vacuum over hydraulic brakes work on a truck that uses hydroboost brakes ?

 

Air>Hydraulic and Vac>Hydraulic both work in much the same way. There is a proportional valve that tees into the trucks hydraulic system and the pressure from that controls the air/vac pressure to the trailer. once at the trailer, another valve controls a booster cylinder on the trailer that converts that vac or air power back into hydraulic pressure that in turn operates the hydraulic drums on the trailer. On the truck side there is also a manual valve for actuating the trailer brakes seperate from the truck brakes. if you go to the second site posted before, there are some diagrams that may help you to draw a mental image of whats going on here.

-Trey

 

Sorry, I didn't see the links.

If I am tapping into the hydraulic system on the rear brakes to get the pressure for the signal the vacuum or air system, then why not just use that pressure to start with ?

 

That is not a very safe thing to do: reason being the truck's brake system has just enough capacity to actuate the 2 cylinders and 2 calipers on the truck. You would be having to activate 6 cylinders and 2 calipers on a system that was designed for half of that load. it would feel like driving around with air in your brake lines. second, if you were to have a hose failure between the truck and trailer (not as uncommon as you might think) you would lose all brake capabilities on the truck and trailer. With either other system, if something happens to the truck system, you have a chance to get stopped with the trailer brakes and if the trailer brakes go south you have a chance to get stopped with the truck brakes.


Getting a pressure signal from the master cylinder like the vac or air systems, and the Brakesmart electric controller do will not cause any increased load on the system. That is because those are just pressure sensors, not an actual set of wheel cylinders that has to be activated. Think of it as an electrical relay of sorts.... it works in much the same way..... its a trigger signal for the vacuum controls.

-Trey

 

One other thing about connecting the trailer directly to the truck hydraulic system is that you have to use some kind couplings or the trailer would have to be connected all the time.

Hyspeed

 

I'd like to see a shadetree jumbled system like that go through a dot check. You'd be calling for the tow truck. If not the coroner.